Biodegradation of Synthetic Base Fluid Surrogates in Gulf of Mexico Sediments under Simulated Deep-Sea Conditions

Abstract

In this study, an anaerobic marine biodegradability test was adapted to study the fate of synthetic base fluid (SBF) surrogates, ethyl oleate and tetradecene, by deep-sea microorganisms. Sediment samples from hundreds of meters deep in the Gulf of Mexico were incubated at low temperatures (4 degrees C) and high hydrostatic pressure in steel vessels. Stimulation of indigenous microbial communities to SBF biodegradation was evident in the fact that the rate of removal of ethyl oleate was greater in sediments that had some previous exposure to SBF (first-order decay coefficient kof -0.22 +/- 0.02 week(-1)) compared to unexposed control sediments (first-order decay coefficient k of -0.11 +/- 0.02 week(-1)). When sulfate-linked tetradecene degradation occurred within the test period, the activity could also be modeled as a first-order decay following an initial lag phase, with an average decay coefficient of k = -0.05 +/- 0.01 week(-1). This study also revealed that the degradation of SBF surrogates by microorganisms collected from deep-sea sediments was not significantly effected by the hydrostatic incubation pressure.